An aircraft fuselage comprises in a known way a hull structure 1 (FIG. 2a) and a floor 2 (FIG. 2b), and is commonly produced by assembling two or more sections.
Each section generally comprises, for hull structure 1, transverse stiffeners, known as frames 3, longitudinal stiffeners, known as stringers 4, attached on these frames 3, and a skin in the form of one or more metal or composite sheets shaped according to the desired section, attached to the frames 3 and stringers 4.
The frames 3 are positioned along sections of the fuselage substantially perpendicular to a longitudinal axis X of the aircraft (FIG. 2a). The stringers 4 extend between the frames 3 substantially along the longitudinal axis X.
The floor 2 is a primary structure inside the hull structure 1 of the fuselage.
Currently and in a known way, a floor section is formed by an assembly of cross members 5, rails 6 (FIG. 2b) secured by screwing, riveting, welding or gluing, depending on the materials, and supporting horizontal covering elements not shown.
The cross members 5 are generally straight and horizontal, in an aircraft reference space, and extend perpendicular to the longitudinal axis X, along a transverse axis Y of the aircraft. Their role is to dissipate the forces related to the load on the floor 2 towards the hull structure 1 of the fuselage. The rails 6 extend along the longitudinal axis X. They are used to fix furniture elements, for example seats.
To achieve the assembly of the hull structure 1 and floor 2, numerous mechanical connections must be made between them.
For example, in order to dissipate forces (mostly the mass of a load on the floor) to the fuselage's hull structure 1, the cross members 5 are attached to the frames 3 at their extremities and frequently by means of braces 7, each bearing a different point 8 of the frame.
In addition, each floor cross member 5 must be lined up accurately to a frame 3 in order to be attached to it.
This relative positioning of the floor 2 with respect to the hull structure 1 is, in the usual embodiments, indeterminate and requires a methodical realization of both the 2 floor and the fuselage when the floor is installed pre-assembled in each section. The frames 5 and cross members 3 are structural elements intended to dissipate significant force flows and each therefore has a high rigidity. As a result, these elements are not able to deform so as to adapt to any misalignments. Compensating for positioning errors during manufacture is therefore difficult.
Finally, according to a recent development, the increasingly widespread use of composites for manufacturing fuselage structures means a fuselage hull structure 1 can be realized in one piece, circumferentially closed, known as a full-barrel composite fuselage. Therefore, the floor 2 and hull structure 1 can no longer be assembled to form a fuselage section by the traditional method of assembling the floor on a lower portion of the structure, known as the tub, before completion of the frames.
Moreover, the positioning of a previously assembled floor in the circumferentially closed hull structure leads to even greater difficulties related to manufacturing tolerances and assembly indeterminacy, since the hull structure closed in this way is extremely rigid and it is impossible to compensate for misalignments through the elastic deformation of the structure.
There is therefore a need for a floor structure able to allow the cost-efficient assembly of said floor in a circumferentially closed hull structure, and allowing slight misalignments between the floor cross members and the frames to be compensated for.
The object of this invention is to propose a new aircraft cabin floor structure associated with a new method of assembling such a floor.